Laminated aramid fiber friction members

Abstract

A laminated friction member, such as a clutch facing comprising a friction element comprising aramid fibers and a reinforcing element formed of non-aramid fibers, the elements being impregnated with and bonded together by means of heat-curable cement.

What is claimed is: 
     
       1. A friction member comprising a friction element formed of aramid fibers having a decomposition temperature of at least 850° F. impregnated with a heat-curable cement and disposed in a configuration to form a first preform, and a reinforcing element comprising non-aramid fibers impregnated with a heat-curable cement and disposed in a configuration to form a second preform, said cement with which said non-aramid fibers are impregnated being compatible with that with which said aramid fibers are impregnated, said first and second preforms having been superimposed one upon the other and subjected to heat and pressure to compress said preforms, to cure said cement and to bond said preforms together to form a unitary friction member. 
     
     
       2. A friction member according to claim 1 in which said aramid fibers are substantially continuous filaments. 
     
     
       3. A friction facing according to claim 1 in which said aramid fibers are staple fibers. 
     
     
       4. A friction member according to claim 1 in which said first preform contains up to about 30 percent, by weight, of non-aramid fibers. 
     
     
       5. A friction member according to claim 1 in which the cement with which the fibers of said first and second preforms are impregnated comprises from about 20 to about 80 percent, by weight, of a thermosetting resin and from about 80 to about 20 percent of a heat-curable elastomer. 
     
     
       6. A friction member according to claim 5 in which said thermosetting resin is a phenol formaldehyde resin, said heat-curable elastomer is a natural rubber, and said resin and elastomer are present in substantially equal quantities in said cement. 
     
     
       7. A friction member according to claim 1 in which said aramid fibers have a decomposition temperature of at least about 900° F. 
     
     
       8. A friction member according to claim 1 in which said aramid fibers are formed of the condensation product of terephthalic acid and p-phenylenediamine, and have a decomposition temperature of about 930° F. 
     
     
       9. A friction member according to claim 1 having molded therein a plurality of holes extending from the exposed surface of said friction element into said reinforcing element, the exposed surface of said reinforcing element having been removed to a depth sufficient to expose said holes. 
     
     
       10. A friction member according to claim 1 in the form of a disc brake pad. 
     
     
       11. A friction member according to claim 1 in the form of a brake lining. 
     
     
       12. An annular friction facing comprising a friction element comprising aramid fibers having a decomposition temperature of at least 850° F. impregnated with a heat-curable cement and disposed so as to form a first annular preform, and a reinforcing element formed of non-aramid fibers impregnated with a heat-curable cement and disposed so as to form a second annular preform, said cement with which said non-aramid fibers are impregnated being compatible with that with which said tape of aramid fibers is impregnated, said first and second preforms having been superimposed one upon the other and subjected to heat and pressure to compress said preforms and to cure said cement to bond said preforms together to form an annular friction facing. 
     
     
       13. A friction facing according to claim 12 in which said aramid fibers are in the form of a tape comprising a plurality of yarns. 
     
     
       14. A friction facing according to claim 12 in which said aramid fibers are in the form of a knitted tape. 
     
     
       15. A friction facing according to claim 13 in which said aramid fibers are substantially continuous filaments. 
     
     
       16. A friction facing according to claim 13 in which said aramid fibers are staple fibers. 
     
     
       17. A friction facing according to claim 12 in which the cement with which the fibers of said first and second preforms are impregnated comprises from about 20 to about 80 percent, by weight, of a thermosetting resin and from about 80 to about 20 percent of a heat-curable elastomer. 
     
     
       18. A friction facing according to claim 17 in which said thermosetting resin is a phenol formaldehyde resin, said heat-curable elastomer is a natural rubber, and said resin and elastomer are present in said cement in substantially equal proportions. 
     
     
       19. A friction element according to claim 12 in which said aramid fibers have a decomposition temperature of at least about 900° F. 
     
     
       20. A friction facing according to claim 12 in which said aramid fibers are formed of the condensation product of terephthalic acid and p-phenylenediamine, and have a decomposition temperature of about 930° F. 
     
     
       21. A friction facing according to claim 12 having molded therein a plurality of holes extending from the exposed surface of said friction element into said reinforcing element, the exposed surface of said reinforcing element having been removed to a depth sufficient to expose said holes. 
     
     
       22. An annular friction facing comprising a friction element formed of a first tape comprising aramid fibers having a decomposition temperature of at least 850° F. impregnated with a heat-curable cement and disposed in an undulating annular fashion to form a first annular preform, and a reinforcing element formed of a second tape comprising substantially continuous glass filaments impregnated with a heat-curable cement and disposed in an undulating annular fashion to form a second annular preform, said cement with which said second tape is impregnated being compatible with that with which said first tape is impregnated, said first and second preforms having been superimposed one upon the other and subjected to heat and pressure to compress said tapes and to cure said cement to bond said preforms together to form an annular friction facing. 
     
     
       23. A friction facing according to claim 22 in which said first tape comprises a plurality of yarns and second tape comprises a plurality of rovings. 
     
     
       24. A friction facing according to claim 22 in which said first tape comprises a knitted tape. 
     
     
       25. A friction facing according to claim 22 in which said second tape comprises a strip of woven fabric. 
     
     
       26. A friction facing according to claim 23 in which said aramid fibers are substantially continuous filaments. 
     
     
       27. A friction facing according to claim 23 in which said aramid fibers are staple fibers. 
     
     
       28. A friction facing according to claim 22 in which said tape of which said first preform is composed contains up to about 30 percent, by weight, of non-aramid fibers. 
     
     
       29. A friction facing according to claim 22 in which said cement with which said first and second tapes are impregnated comprises from about 20 to about 80 percent, by weight, of a thermosetting resin and from about 80 to about 20 percent of a heat-curable elastomer. 
     
     
       30. A friction facing according to claim 8 in which said thermosetting resin is a phenol formaldehyde resin, said heat-curable elastomer is a natural rubber, and said resin and elastomer are present in said cement in substantially equal proportions. 
     
     
       31. A friction facing according to claim 22 in which said aramid fibers have a decomposition temperature of at least about 900° F. 
     
     
       32. A friction facing according to claim 22 in which said aramid fibers are formed of the condensation product of terephthalic acid and p-phenylenediamine, and have a decomposition temperature of about 930° F. 
     
     
       33. A friction facing according to claim 22 having molded therein a plurality of holes extending from the exposed surface of said friction element into said reinforcing element, the exposed surface of said reinforcing element having been removed to a depth sufficient to expose said holes. 
     
     
       34. The method of forming an annular friction facing comprising: (A) forming a first tape comprising aramid fibers having a decomposition temperature of at least 850° F. impregnated with a heat-curable cement and disposing said tape in spiral or undulating annular fashion to form a first disc-shaped preform,   (B) forming a second tape comprising substantially continuous glass filaments impregnated with a heat-curable cement and disposing said tape in spiral or undulating annular fashion to form a second disc-shaped preform, said cement with which said second tape is impregnated being compatible with that with which said first tape is impregnated,   (C) superimposing said first and second preforms one upon the other and subjecting said superimposed preforms to heat and pressure to compress said tapes and to cure said cement to bond said preforms together to form a unitary disc-shaped friction facing.   
     
     
       35. The method according to claim 34 in which said first tape comprises a plurality of yarns and second tape comprises a plurality of rovings each impregnated with heat-curable cement. 
     
     
       36. The method according to claim 34 in which said first tape comprises a knitted tape. 
     
     
       37. The method according to claim 34 in which said second tape comprises a strip of woven fabric. 
     
     
       38. The method according to claim 35 in which said aramid fibers are substantially continuous filaments. 
     
     
       39. The method according to claim 35 in which said aramid fibers are staple fibers. 
     
     
       40. The method according to claim 34 in which said tape of which said first preform is composed contains up to about 30 percent, by weight, of non-aramid fibers. 
     
     
       41. The method according to claim 34 in which said cement with which said first and second tapes are impregnated comprises from about 20 to about 80 percent, by weight, of a thermosetting resin and from about 80 to about 20 percent of a heat-curable elastomer. 
     
     
       42. The method according to claim 41 in which said thermosetting resin is a phenol formaldehyde resin, said heat-curable elastomer is a natural rubber, and said resin and elastomer are present in said cement in substantially equal proportions. 
     
     
       43. The method of claim 34 in which said aramid fibers have a decomposition temperature of at least about 900° F. 
     
     
       44. The method according to claim 34 in which said aramid fibers are formed of the condensation product of terephthalic acid and p-phenylenediamine, and have a decomposition temperature of about 930° F. 
     
     
       45. The method of forming a disc-shaped friction facing having an inner diameter and an outer diameter for use in a clutch assembly or the like comprising the steps of: (A) (1) impregnating a plurality of yarns comprising aramid fibers having a decomposition temperature of at least about 850° F. with a heat-curable cement;   (2) drying said cement;   (3) combining a plurality of said dry, cement-impregnated aramid fiber yarns to form a first tape; and   (4) winding said first tape in undulating fashion to form a first disc-shaped preform;   (B) (1) impregnating a plurality of rovings of substantially continuous glass filaments with a heat-curable cement which is compatible with the cement with which said first tape is impregnated;   (2) drying said cement;   (3) combining a plurality of said dry cement-impregnated glass fiber rovings to form a second tape; and   (4) winding said second tape in undulating fashion to form a second disc-shaped preform;   (C) (1) superimposing said first and second preforms one upon the other, and   (2) subjecting said superimposed preforms to heat and pressure to compress said tapes and to cure said cement to bond said preforms together to form a unitary disc-shaped friction facing.   
     
     
       46. The method according to claim 45 in which said aramid fibers are substantially continuous filaments. 
     
     
       47. The method according to claim 45 in which said aramid fibers are staple fibers. 
     
     
       48. The method according to claim 45 in which said tape of which said first preform is composed contains up to about 30 percent, by weight, of non-aramid fibers. 
     
     
       49. The method according to claim 22 in which said cement with which said first and second tapes are impregnated comprises from about 20 to about 80 percent, by weight, of a thermosetting resin and from about 80 to about 20 percent of a heat-curable elastomer. 
     
     
       50. The method according to claim 49 in which said thermosetting resin is a phenol formaldehyde resin, said heat-curable elastomer is a natural rubber, and said resin and elastomer are present in said cement in substantially equal properties. 
     
     
       51. The method of claim 45 in which said aramid fibers have a decomposition temperature of at least about 900° F. 
     
     
       52. The method according to claim 22 in which said aramid fibers are formed of the condensation product of terephthalic acid and p-phenylenediamine, and have a decomposition temperature of about 930° F. 
     
     
       53. The method according to claim 45 in which said preforms are subjected to heat and pressure in a mold having a plurality of pins which extend through said first preform and into said second preform during the molding operation, and in which the surface of the molded disc-shaped friction facing comprising glass fibers is ground to a sufficient depth to expose the holes molded into said friction facing by means of said pins.